A ventilator delivers a flow of pressurized gas, such as air and/or a mixture of air and extra (supplemental) oxygen, to the airway of a patient in order to assist in or substitute for the patient's breathing. A ventilator operates cyclically, such that the gas is provided to the patient during an inspiratory phase (corresponding to inhalation) and received from the patient during a subsequent expiratory phase (corresponding to exhalation). A sidestream gas analyzer diverts a portion of the patient's respired gases, which are inhaled and exhaled by the patient (respiratory gas stream) during mechanical ventilation or normal respiration, to a sensor, such as a gas analysis bench, through sampling tubes, including a patient airway interface and an extension line, for example.
The sensor may be used to detect and analyze at least one gas in the respiratory gas stream, such as carbon dioxide (CO2). However, the presence of moisture generally affects the accurate detection of the various gases in the respiratory gas stream. A water filter or water trap is used to remove or reduce the moisture from the respiratory gas stream. The water filter or trap is often included among patient accessories in a disposable patient interface of a conventional sidestream respirator gas analysis system, and is therefore discarded after each use, along with other patient accessories, such as the airway and a cannula, for example. In addition, a sampling chamber receives the dried respiratory gas stream from the water trap filter and presents the sample gas in a controlled volume to the sidestream gas analysis bench for analysis. Similar to the water trap, the sampling chamber may also be included in the patient interface of a conventional sidestream respirator gas analysis system, and thus is discarded after each use. Such sidestream sampling accessories burden the disposable patient interface with the cost of the water trap and sampling chamber.